Communication between physicians caring for hospitalized patients and those patients'primary care providers (PCPs) is often suboptimal. Hospital-based information systems can improve communication by automating information exchange between hospital physicians and PCPs, and perhaps, as a result, improve the quality and safety of health care. MedTrak, the University of Pittsburgh Medical Center (UPMC) electronic physician communication tool, has proven successful and is poised to move forward with an initiative we call virtual continuity, allowing PCPs to follow their patients electronically if they cannot do so physically. Virtual continuity will include: emails to PCPs triggered by clinical events with embedded links to electronic medical record data and communication portals, medication lists electronically delivered to PCPs at admission and discharge, and immediate PCP notification of discharge with pertinent clinical details. To evaluate virtual continuity, we will examine the frequency of discharge medication errors in complex medical patients using a cluster randomized study design of virtual continuity compared to usual communication. Medication errors will be ascertained using accepted methods. We will also investigate differences in rehospitalization, post discharge emergency department visit and PCP follow up rates, as well as patient and PCP satisfaction with hospital communication. The IT cost of implementing and maintaining the virtual continuity intervention will also be assessed. Virtual continuity will allow PCPs to participate more directly in the care of their hospitalized patients. Improved communication could lead to higher-quality patient care and greater patient care safety for hospitalized patients with complex medical problems.